On the role of processing parameters in thermal behavior, surface morphology and accuracy during laser 3D printing of aluminum alloy

Abstract

In this paper, a 3D mesoscopic model was established using the finite volume method (FVM) to investigate the process of powder-to-solid transition under different processing parameters during the selective laser melting (SLM) of AlSi10Mg powder, taking into account the initial feeding powder material and the attendant significant complexity of the physical interaction between the powder and laser beam. The effects of different processing parameters on the temperature field, velocity field, surface morphology and Z-direction shrinkage were also studied. It was found that both high and low laser power resulted in a rough surface quality and there were optimal processing parameters (P = 250 W, v = 400 mm s−1, d = 50 μm) for AlSi10Mg powder to get a relatively smooth surface and reasonable shrinkage value. That is because low laser power could not melt the powder completely and high laser power caused excessive liquid formation which developed into so-called ‘self-balling’. Meanwhile, it was interesting to find that the temperature rebounding phenomenon was produced, relieving the formation of large residual stress due to the self-heat-treatment. In order to further study ‘self-balling’ under a long irradiation time, the melt process of particles at a static laser beam is simulated, demonstrating that the volume energy density played a key role in ‘self-balling’. Experimental findings were compared with simulation results and they showed good agreement.